In the past, there has been known a system which uses shapes and dimensions (models) and movement data (machining program) of members which move relative to each other at a tool side and a workpiece side of a machine tool to check for an interference between the members when the machine tool is operated (for example, see Patent Literature 1). In the system described in Patent Literature 1, when storing a workpiece model in a memory, when the dimensions, position, and posture of a workpiece are input, it is assumed that a workpiece having the predetermined dimensions is mounted at a predetermined position of the machine tool.
However, workpieces which are mounted at a machine tool vary in dimensions, positions, and postures. In order to execute an accurate check for interference, it is necessary to measure the actually mounted workpieces for dimensions, positions, and postures and input these as modeling data. This took trouble and time. Further, the judgment of interference is poor in precision.